1. Field of the Invention
Aspects of the present invention relate to a rechargeable battery. More particularly, aspects of the present invention relate to a rechargeable battery including a cap assembly having an improved structure.
2. Description of the Related Art
Rechargeable batteries can be repeatedly charged and discharged, unlike primary batteries, which are incapable of being recharged. Low capacity rechargeable batteries composed of a single cell are generally used for portable small electronic devices, such as mobile phones, laptop computer, and camcorders. Large capacity rechargeable batteries composed of a plurality of cells connected in the form of a pack are widely used to drive motors for hybrid electric vehicles. Such a rechargeable battery is manufactured in various forms. The representative form of such a rechargeable battery is a cylindrical form or a quadrilateral form. Such rechargeable batteries are serially connected to form a rechargeable battery module or battery pack to drive the motor of an electric vehicle, which needs a large amount of electric power.
A typical rechargeable battery includes an electrode assembly having an anode and a cathode with a separator interposed therebetween, a case that provides a space to house the electrode assembly, and a cap assembly that closes and seals the case.
In the case of a rechargeable battery formed in a cylindrical shape, an anode uncoated region and a cathode uncoated region where an active material is not coated are formed at the anode and the cathode of the electrode assembly, respectively. The anode uncoated region and the cathode uncoated region are disposed to face in different directions.
A cathode current collecting plate is adhered on the cathode uncoated region, and an anode current collecting plate is adhered on the anode uncoated region. Each of the cathode current collecting plate and the anode current collecting plate is electrically connected to the case or the cap assembly to guide the current to the outside. For example, the cathode electrode current collecting plate may be electrically connected to the case and the anode current collecting plate may be electrically connected to the cap assembly. Alternatively, the cathode electrode current collecting plate may be electrically connected to the cap assembly and the anode current collecting plate may be electrically connected to the case.
The case acts as a cathode terminal when the cathode current collecting plate is electrically connected to the case. A cap plate of the cap assembly acts as an anode terminal when the anode current collecting plate is electrically connected to the cap assembly.
A vent plate is disposed in the cap assembly. The vent plate interrupts an electrical connection between the cap assembly and the electrode assembly if an undesirable or unexpected reaction occurs in the rechargeable battery. In particular, if the pressure of the rechargeable battery becomes greater than a predetermined value, the vent plate is curved outward and a welded portion of the vent plate becomes separated from a portion of the cap assembly that is electrically connected to the electrode assembly. Accordingly, the electrical connection between the electrode assembly and the cap plate is interrupted.
If the pressure increases by an undesirable or unexpected reaction in the rechargeable battery and the vent plate is separated from the cap assembly, an electrical arc may be generated between the separated vent plate and the cap assembly. The electrical arc produces a lot of heat, and thus the temperature of the rechargeable battery increases. In some cases, the electrical arc and increased temperature can cause an explosion of the rechargeable battery.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. In other words, the inclusion of information in this Background section is not to be construed as a representation that any of such information is prior art.